Add missing stdio.h header in files using scanf/sscanf function.

Various files in webrtc codebase use scanf/sscanf function without
including stdio.h header file which is supposed to define it. This
somehow works when using glibc, but fails with uClibc.

Bug: webrtc:8641
Change-Id: Ie4ae17af32b32ed8cea567166b6b0e5193966995
Reviewed-on: https://webrtc-review.googlesource.com/32261
Commit-Queue: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21775}

AUTHORS

@@ -81,3 +81,4 @@ The WebRTC Authors <*@webrtc.org>
 Vonage Holdings Corp. <*@vonage.com>
 Wire Swiss GmbH <*@wire.com>
 Miguel Paris <mparisdiaz@gmail.com>
+Vewd Software AS <*@vewd.com>

media/engine/videoencodersoftwarefallbackwrapper.cc

@@ -10,6 +10,7 @@
 
 #include "media/engine/videoencodersoftwarefallbackwrapper.h"
 
+#include <cstdio>
 #include <utility>
 
 #include "media/base/h264_profile_level_id.h"

modules/bitrate_controller/send_side_bandwidth_estimation.cc

@@ -12,6 +12,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <cstdio>
 #include <limits>
 #include <string>
 

modules/congestion_controller/delay_based_bwe.cc

@@ -12,6 +12,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <cstdio>
 #include <string>
 
 #include "logging/rtc_event_log/events/rtc_event_bwe_update_delay_based.h"

modules/congestion_controller/send_side_congestion_controller.cc

@@ -11,6 +11,7 @@
 #include "modules/congestion_controller/include/send_side_congestion_controller.h"
 
 #include <algorithm>
+#include <cstdio>
 #include <memory>
 #include <vector>
 

modules/pacing/alr_detector.cc

@@ -12,6 +12,7 @@
 
 #include <algorithm>
 #include <string>
+#include <cstdio>
 
 #include "logging/rtc_event_log/events/rtc_event_alr_state.h"
 #include "logging/rtc_event_log/rtc_event_log.h"

modules/remote_bitrate_estimator/aimd_rate_control.cc

@@ -13,6 +13,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cmath>
+#include <cstdio>
 #include <string>
 
 #include "rtc_base/checks.h"

modules/remote_bitrate_estimator/overuse_detector.cc

@@ -12,6 +12,7 @@
 
 #include <math.h>
 #include <stdlib.h>
+#include <stdio.h>
 
 #include <algorithm>
 #include <sstream>

video/overuse_frame_detector.cc

@@ -12,6 +12,7 @@
 
 #include <assert.h>
 #include <math.h>
+#include <stdio.h>
 
 #include <algorithm>
 #include <list>